ramips: mt7620: power up ephy port 4

In some boards port 4 of mt7620 switch is powered down in bootloader
configuration as lan/wan package leak mitigation.

Reset ephy port 4 to default settings to power up the port.

Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
[clarify issue in commit message]
Signed-off-by: Mathias Kresin <dev@kresin.me>

target/linux/ramips/files-4.14/drivers/net/ethernet/mtk/gsw_mt7620.c

@@ -166,6 +166,7 @@ static void mt7620_hw_init(struct mt7620_gsw *gsw, struct device_node *np)
 		_mt7620_mii_write(gsw, 4, 30, 0xa000);
 		_mt7620_mii_write(gsw, 4, 4, 0x05e1);
 		_mt7620_mii_write(gsw, 4, 16, 0x1313);
+		_mt7620_mii_write(gsw, 4, 0, 0x3100);
 		pr_info("gsw: setting port4 to ephy mode\n");
 	}
 }

target/linux/ramips/files-4.9/drivers/net/ethernet/mtk/gsw_mt7620.c

@@ -166,6 +166,7 @@ static void mt7620_hw_init(struct mt7620_gsw *gsw, struct device_node *np)
 		_mt7620_mii_write(gsw, 4, 30, 0xa000);
 		_mt7620_mii_write(gsw, 4, 4, 0x05e1);
 		_mt7620_mii_write(gsw, 4, 16, 0x1313);
+		_mt7620_mii_write(gsw, 4, 0, 0x3100);
 		pr_info("gsw: setting port4 to ephy mode\n");
 	}
 }